This invention relates to percussion-ignitable primers.
As discussed in "The Gun and Its Development," 9th edition, by W. W. Greener, at pages 116-117, tube primers were known in the early 19th century. A tube primer in general use during this period comprised a tube filled with a detonating powder, the tube being adapted to be placed in the touch hole of a gun and exploded by a blow of the cock on the side of the tube. This form of tube primer did not include an anvil and required support for the lower surface of the tube opposite the cock.
A more recent development in the primer art is the tube primer utilized in flash cubes introduced in the last decade. The construction of this primer, together with its relationship to a flash cube, is depicted in FIGS. 1 and 2. This primer is generally constituted by a metal ignition tube 14 and a wire anvil 16 extending therethrough in coaxial relationship therewith. Upon the wire anvil 16 is a coating 18 of primer material which is spaced from the interior wall of the tube 14 by a narrow clearance. Ignition and deflagration of the primer material coated on the wire anvil 16 is usually beget by a wire striking the tube at right angles to its axis to slightly deform the tube and thereby crush a portion of the material.
An obvious disadvantage in the above described primer construction is that two elements must be provided, viz.: The metal tube and the wire anvil. In addition, structure must be provided for centering the anvil properly within the tube to insure ignition thereof when the tube is struck. Moreover, in such a primer the only passage for the flame to proceed through is that annular space between the outer periphery of the anvil and the inner periphery of the tube. Furthermore, it has been found that when a primer such as that shown in FIG. 1 is employed to ignite a delay cord, there is a tendency for the primer to blow off the cord due to over-pressurization.